Occluder with Access Passage and Closure Thereof

The present application is a continuation of U.S. patent application Ser. No. 18/644,723, filed Apr. 24, 2024, which is a continuation of U.S. Pat. No. 11,998,183, filed Oct. 24, 2023, which is a continuation of U.S. Pat. No. 12,059,142, filed Jul. 1, 2022, which is a continuation of U.S. Pat. No. 11,832,805, filed Aug. 26, 2020, which claims the benefit of priority to U.S. Provisional Patent Application No. 62/891,542, filed Aug. 26, 2019, the entire contents and disclosures of which are hereby incorporated by reference herein.

The present disclosure relates generally to medical devices that are used in the human body. In particular, the present disclosure is directed to embodiments of a closure device or occluder that includes an access passage and at least one closure of the access passage, and methods of making and using the same. The embodiments and methods disclosed herein enable access through the occluder subsequent to deployment of the occluder within the body.

Atrial Septal defects (ASD) include heart defects that allow blood to flow between the left and right atria of the heart, decreasing cardiac output. In at least some cases, ASD are closed using an occlusive closure device, such as the Amplatzer™ Septal Occluder (ASO). Occluders are generally formed from braided metal fabrics or wire with mesh. Some of these known occluders are shown in. As illustrated, conventional occludersare formed with discsthat engage a surface of the septal wall that separates the left and right atria. These discscan range in size from 10 mm to 54 mm in diameter and are conventionally formed of continuous metal fabric or wire. As such, these discsform a substantially impenetrable surface, in particular for smaller-size occluders.

Several percutaneous procedures, which may be performed after an occluder has been deployed, require access to the left atrium across the septal wall. For example, a younger patient may have an occluder deployed to close an ASD, but may subsequently develop atrial fibrillation (AFIB). A physician may need to map and/or ablate tissue in the left atrium, and may therefore need to cross the septal wall. Where a conventional occluder has already been deployed, the physician may be unable to penetrate the discs (e.g., discsshown in) to cross the septal wall at the existing opening therethrough (i.e., the ASD).

Accordingly, it would be desirable to have an occlusive closure device that enables subsequent access for passage of medical devices therethrough, including procedural devices and/or devices to create shunting and/or fenestrations.

Moreover, a rare, but adverse event that has been reported to occur in some occluder implantations is erosion of the atrial wall tissue. The result of this tissue erosion can be removing the device, fixing eroded holes and/or surgically closing defects.

Accordingly, it would be desirable to reduce or eliminate erosion of cardiac tissue while maintaining the fundamental function and effectiveness of an occluder.

The present disclosure generally relates to a closure device or occluder including an access passage. The present disclosure discloses such devices and methods of forming and using the same to, for example, enable access for medical devices therethrough after the closure device has been deployed in the human body. The occluder having the access passage further facilitates reducing erosion of cardiac tissue by reducing radial forces applied thereto.

In at least one aspect of the present disclosure, an occlusive medical device is provided. The occlusive medical device includes a frame and at least one closure coupled to the frame. The frame includes a distal annular flange having a radially outer surface and a radially inner surface, a proximal annular flange having a radially outer surface and a radially inner surface, and a waist portion extending between and connecting the distal annular flange to the proximal annular flange. The radially inner surface of the distal annular flange, the waist member, and the radially inner surface of the proximal annular flange define an unobstructed passageway through the frame. The at least one closure is configured to close the passageway to: (i) provide an occlusive effect, and (ii) enable subsequent access through the passageway when the occlusive medical device is deployed at a target site.

The foregoing and other aspects, features, details, utilities and advantages of the present disclosure will be apparent from reading the following description and claims, and from reviewing the accompanying drawings.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. It is understood that that Figures are not necessarily to scale.

The present disclosure relates generally to medical devices that are used in the human body. In particular, the present disclosure generally relates to occluders including an access passage for access through the occluder (e.g., by a medical device) subsequent to deployment of the occluder within a patient's body. The occluders also include a closure that serves an occlusion function but that is penetrable to allow access through the access passage. As used herein, “access” refers broadly to access to and/or through the access passage by any medical device performing any function. Accordingly, “access” may refer to access by a medical device such as a catheter that is passed completely through the occluder, as well as to access by a medical device such as a device configured to create a fenestration in the occluder (e.g., a dilator, balloon, etc.).

The disclosed embodiments may lead to more consistent and improved patient outcomes. It is contemplated, however, that the described features and methods of the present disclosure as described herein may be incorporated into any number of systems as would be appreciated by one of ordinary skill in the art based on the disclosure herein.

The present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the disclosure are shown. Indeed, this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

Some embodiments of the present disclosure provide a medical device, such as an occlusion device (occluder), for use in occluding an abnormality in a patient's body, such as an Atrial Septal Defect (ASD), a Ventricular Septal Defect (VSD), a Patent Ductus Arteriosus (PDA), a Patent Foramen Ovale (PFO), conditions that result from previous medical procedures such as Para-Valvular Leaks (PVL) following surgical valve repair or replacement, and the like. The device may also be used as a flow restrictor, pressure release device, or an aneurysm bridge or other type of occluder for placement in the vascular system. It is understood that the use of the term “abnormality” is not meant to be limiting, as the device may be configured to occlude any vessel, organ, opening, chamber, channel, hole, cavity, or the like, located anywhere in the body.

Some embodiments of the present disclosure provide an improved percutaneous catheter directed intravascular occlusion device for use in the vasculature in patients' bodies, such as blood vessels, channels, lumens, a hole through tissue, cavities, and the like, such as an ASD or VSD. Other physiologic conditions in the body occur where it is also desirous to occlude a vessel or other passageway to prevent blood flow into or therethrough. These device embodiments may be used anywhere in the vasculature where the anatomical conditions are appropriate for the design.

The medical device may include one or more occlusive materials, which are configured to substantially preclude or occlude the flow of blood so as to facilitate thrombosis. As used herein, “substantially preclude or occlude flow” shall mean, functionally, that blood flow may occur for a short time, but that the body's clotting mechanism or protein or other body deposits on the occlusive material results in occlusion or flow stoppage after this initial time period. According to one embodiment of the present disclosure, the device is configured to occlude at least a portion of a vessel, a channel, a lumen, an opening, or a cavity in less than about 10 minutes and even less than about 5 minutes with observed occlusions in testing as low as within about 1 minute. Thus, in one embodiment, there is not “immediate occlusion,” as the device does not immediately obstruct all blood flow but, rather, slows the flow of blood in order for occlusion to occur as described above. Such immediate occlusion may result in problems in fixation or positioning of the device in the lumen or may result in suction or the complete stoppage of flow which may be undesirable in some circumstances.

, by way of example, illustrate an exemplary embodiment of a medical devicein accordance with the present disclosure. The medical deviceis specifically embodied as an occluder. The occluderincludes a frameand at least one closure. More particularly, the framehas an outer shape such that, when the occluderis deployed, the frameconforms to the tissue (not shown in) in which the occluderis deployed.

In one embodiment, the frameincludes two annular flanges,, specifically a left atrial or distal flangeand a right atrial or proximal flange. The annular flanges,are connected by a waist member. The occluderdefines an open or substantially open passagewaythat extends through the occluder. Specifically, the passagewayextends through the distal annular flange, the waist member, and the proximal annular flange. The annular flanges,therefore have a radially outer surfacewith an outer diameter DO and a radially inner surfacewith an inner diameter D, where the radially inner surfacepartially defines the passageway(and generally corresponds to an inner surfaceof the waist member). In this way, annular flanges,are considered “open,” as contrasted with closed discs (e.g., discs, shown in).

When the occluderis deployed to occlude a defect (e.g., an ASD, VSD, and the like), as described further herein, the occluderis positioned within a hole in the septal wall. The distal annular flangeis positioned on a distal side of the septal wall (i.e., within the left atrium) and engages a distal surface of the septal wall. The proximal annular flangeis positioned on a proximal side of the septal wall (i.e., within the right atrium) and engages a proximal surface of the septal wall. The waist memberextends between and connects the annular flanges,. An outer surface of the waist memberengages and conforms to a surface of the ASD. The occluderis radially flexible but still exerts a suitable clamping force to maintain engagement and conformity with the local tissue, which may reduce the risk of erosion. Each of the annular flanges,and the waist memberexhibit radial flexibility and improved conformance with local tissue, as compared to conventional occluders.

The outer diameter DO of the annular flanges,is greater than a diameter of the ASD in which the occluderis deployed, and the inner diameter Dis less than the outer diameter DO. In some embodiments, the inner diameter Dis sized such that the occluder, specifically the passageway, may enable access therethrough of delivery devices having sizes from 4 French (Fr) to 36 Fr. It should be readily understood that the outer diameter Dand/or the inner diameter Dmay vary based on the overall size of the occluderand/or the defect (e.g., the ASD) in which the occluderis to be deployed, which may limit the size of medical devices that may be maneuvered through passageway.

In some embodiments, Dis about 5 mm to about 20 mm larger than D. In some embodiments, the ratio of the area defined by the radially outer surface(i.e., π*(½ D)) and the area defined by the radially inner surface(i.e., π*(½ D)) is about 2:1, such that the passageway(partially defined by the radially inner surface) constitutes about 50% of a surface area of a respective planar facedefined by each annular flange,. It should be well understood that the passagewaymay constitute more or less than 50% of the surface area of this planar face, as long as the passagewayis sufficiently sized to enable access therethrough to various medical devices, such as catheters. In the exemplary embodiment, the passagewayconstitutes from about 20% to about 90% of the surface area of each annular flange,, and, more preferably, may constitute from about 50% to about 70% of the surface area of each annular flange,.

By forming the framewith annular flanges,(contrasted with closed discs, such as discs), the framemay experience reduced radial hoop stress (e.g., due to the relative lack of rigid metal material in the center thereof). As such, the occludermay exert less radial force on local tissue when the occluderis deployed. Accordingly, the occludermay reduce the risk of erosion of the local tissue compared to conventional occluders. Moreover, the reduction in material in the framemay reduce production cost of the occluder.

The framemay be formed from any suitable material. In at least some exemplary embodiments, the frameis formed from at least one layer of braided metal material. In particular, the frameis formed from a shape memory material, such as nitinol. In some embodiments, the frameis formed from one or multiple layers of braided nitinol wires—for example, by folding one layer over itself to form two layers. Such a material may include, in some embodiments, from 36 to 288 wires. The framemay be formed from non-braided materials, including shape memory alloys. For example, a shape memory alloy may be laser-cut and heat-set, or at least one formed wire (e.g., from 1 to 50 such wires) may be wrapped about a mandrel and heat-set. In some embodiments, a helical angle formed by the wire(s) of the frame(e.g., braided and/or wound formed wires) may be selected to optimize a hoop strength and clamping force of the frame. This optimization may further reduce the radial force applied to local tissue when the occluderis deployed, as described above.

Alternatively, the frameis formed from a non-shape memory material and may be deployed using a balloon expander. In such embodiments, the framemay be formed from cobalt, stainless steel, chromium, and/or other such medical-grade metallic materials. Alternatively, the framemay be formed from a polymeric material, such as plastic (e.g., injection-molded plastic, bioabsorbable polymers or plastics, etc.). It is contemplated that having a radiopaque (e.g., metallic, radiopaque plastic, etc.) and/or echogenic frame may facilitate more accurate deployment and/or subsequent identification of the location of the occluder.

In the embodiment illustrated in, the frameis a unitary, single-piece frame in which the annular flanges,are integral with the waist member. In such embodiments, the framemay be formed from a single material. In other embodiments, such as the embodiment illustrated in, the annular flanges,are formed separately from the waist memberand are subsequently attached to the waist memberto form the frame. The waist member, in some embodiments, is the same material as the annular flanges,, but in other embodiments, the waist memberis formed from a different material than the annular flanges,. The waist membermay be attached to the annular flanges,by sutures or sewing, welding, fasteners, adhesives, over-molding, insert molding, and/or any other suitable attachment method.

In the exemplary embodiment of the occluder, the at least one closureis attached to the frameto close or restrict access (e.g., of bodily fluids) through the passagewayof the occluder. In this way, the closureensures the occluderperforms its occlusive function, as described above herein. However, the closureis formed from an occlusive, yet penetrable material, such that access through the passagewayof the occluderby medical devices is not restricted. In the exemplary embodiment, a “penetrable” material is more easily punctured, separated, slit, pierced, or otherwise penetrated than the material that forms the frame.

In the illustrated embodiment of, the closureincludes a first or distal closureand a second or proximal closure. The distal closureis attached to the distal annular flangeat the radially inner surfacethereof. Likewise, the proximal closureis attached to the proximal annular flangeat the radially inner surfacethereof. In this way, each closure,closes passageway.

Each closure,is sized and shaped to substantially cover the passagewayat each annular flange,. The closures,may therefore be circular and have a diameter Dc that is greater than or substantially equal to the inner diameter Dof the respective annular flange,to which it is coupled. Closures(including closures,), as described further herein, may have a diameter Dc that is substantially greater than the inner diameter D. For example, the diameter Dc may be greater than or substantially equal to the outer diameter Dof the respective annular flange,to which it is coupled. Alternatively, the closuremay have a non-circular shape.

In particular,illustrates various sizes, shapes, and locations of closureswith respect to the frameof the occluder. The occludermay include one, two, or three discrete closures. A closuremay be coupled to a flange at any location on an outer surface of the respective flange, such as adjacent the passageway, at the outer diameter of the flange, at some intermediate location, and/or at a surface of the flange that engages with the septal wall when the occluderis deployed. A closuremay additionally or alternatively be coupled to the waist memberof the occluderat a position intermediate the annular flanges,. A closuremay additionally or alternatively fully enclose the occluder.

A closureis attached to the frameusing any suitable method, such as by suture or sewing, bonding (with other polymers, thermally, via laminating, etc.), welding, adhering, folding and/or trapping the closurewithin the material of the frame, over-molding, any combination thereof, and/or any other suitable attachment mechanism. In the exemplary embodiment, therefore, the closureis operable in tandem with the frameduring deployment (including loading, advancement, and/or recapture, as described further herein) of the occluder, such that the closurecollapses and expands as the framecollapses expands.

The closuremay be formed from any suitable material. It is contemplated that a bioabsorbable material that promotes endothelialization may be used to form the closure. After the occluderis deployed, the bioabsorbable material will be absorbed while tissue grows over the occluder. Therefore, the passagewaywill be accessible through a relatively soft, thin layer of tissue. Such bioabsorbable materials may include polylactic acid (PLA), poly-L-lactic acid (PLLA), poly lactic-co-glycolic acid (PLGA), polycaprolactone (PCL), combinations thereof, and/or any suitable bioabsorbable material. Alternatively, the closureis at least partially non-bioabsorbable, and may be formed from polyester, polyethylene terephthalate (PET), silicone, urethane, combinations thereof, other polymers, and the like. The closuremay, in some embodiments, be formed in part with a bioabsorbable material and in part with a non-bioabsorbable material. The closuremay be formed from a woven, knitted, or braided material, a printed material, a molded material, and the like. The closuremay be formed from a material suitable to form a fenestration therein, after the occluderis deployed. For example, a medical device configured to create a fenestration (e.g., a dilator, a balloon expander, etc.) may be used to penetrate the closureand create a fenestration therein (e.g., to enable blood flow through the occluder). The closuremay be formed from a material that will remain open after such a procedure.

In some embodiments, the closureis flexible, which may simplify deployment of the occluder, as described further herein, and which may improve the penetrability of the closure(contrasted with the more rigid, dense nitinol mesh that forms discs). In certain embodiments, however, the closuremay include one or more rigid reinforcement elements (not shown). These reinforcement elements may assist deployment of the occluderby ensuring proper orientation of the closureas the occluderis deployed. In some such embodiments, the reinforcement elements are not bioabsorbable. In other embodiment, the reinforcement elements are bioabsorbable at a different rate than the flexible portion(s) of the closure.

In the illustrated embodiment, the occluderalso includes an attachment member. The attachment memberfacilitates deployment of the occluder. As described further herein, the attachment memberis coupled to a delivery cable to advance the occluderthrough a delivery catheter to a target location (e.g., an ASD). The attachment memberremains coupled to the delivery cable until proper positioning of the occluderis confirmed. That is, the attachment memberfacilitates re-positioning and/or recapture of the occluderduring deployment. The attachment membermay include a screw-like member having internal or external threads, a tether-like member, a hoop, a hook, a ball-and-loop type coupler, and/or any suitable attachment membersuch that the occluderis recapturable during deployment. The attachment membermay be formed from a bioabsorbable material.

In some embodiments, the attachment memberis coupled to the framevia one or more spokesextending radially inward from the radially inner surfaceof one or more of the annular flanges,. The spokesmay be integrally formed with the frameand/or may be attached to the frameafter the frameis formed. In the embodiment illustrated in, the occluderincludes four spokes. The occludermay include any suitable number of spokes, such as three, five, or more spokes. For example, in the embodiment illustrated in, the occluderincludes three spokes. The spokesin this embodiment are integral with the frameand formed from the same braided shape-alloy material of the frame.illustrates a similar embodiment including four spokes. Integral spokesmay be formed by extending portions of the braided material (e.g., as shown in) or, in other embodiments, any material used to form the frame. Alternatively, integral spokesmay be formed by forming the corresponding annular flange (e.g., the proximal annular flange) as a fully closed discof material and cutting out portions therefrom to form the spokes(e.g., as shown in). Although the embodiments illustrated indepict the spokespositioned at the proximal angular flange, spokesmay be positioned at (e.g., extend from or be coupled to) the distal annular flangeand/or the waist memberwithout departing from the scope of the present disclosure. Moreover, spokesmay be substantially the same or may have differing lengths, shapes, orientations, and the like.

As described above, spokesmay be formed integrally with the frame, as continuations of the material of frame, or may be coupled to the frame. In some embodiments, spokesmay be formed from suture material, bio-absorbable material, and/or any suitable material. Spokesmay assist with recapture and/or re-positioning of the occluderduring deployment thereof. In some embodiments, the occluderincludes a reinforcement member (not shown) coupled to the radially inner surfaceof an annular flange (e.g., the proximal annular flange) where the spokesare coupled thereto. This reinforcement member may protect the closurefrom the ends of the spokes, to prevent these ends of the spokesfrom puncturing the closure. The reinforcement member may be formed from any suitable material, such as the same material of the closure(e.g., a double layer of the closure material), or any other material.

In other embodiments, the attachment memberis coupled to the closure. For example, the attachment membermay be sewn, adhered, welded, and/or otherwise attached to the closure. In still other embodiments, the attachment membermay be formed integrally with the closure. For example, where the closureis formed from a molded material, the attachment membermay be molded (e.g., as a threaded member or a hoop). In some embodiments, where the attachment memberis not attached to the frame, the occludermay include no spokes, which may maximize the passagewayand enhance accessibility through the occluderafter deployment thereof.

Although the attachment memberis shown in a center of the occluderin, it should be readily understood that the attachment membermay be positioned in a non-central location without departing from the scope of the present disclosure.

In some embodiments in which the occluderincludes spokeson the proximal annular flange, a closuremay be coupled to that proximal annular flangevia the spokes. For example, as shown in, the spokesdefine through-holesto the passageway, and each through-holehas a corresponding closurecoupled thereacross. These closuresare coupled to the framealong the spokes.

Turning now to, an occluderin accordance with the present disclosure is shown within a delivery device. Specifically, the occluderis shown in a collapsed configuration (where the occluder is shown in an expanded or deployed configuration in) within a delivery sheath. A delivery cableis coupled to the attachment membersuch that the occludermay be advanced through the delivery sheathto a target location for deployment (e.g., within an ASD). A similar embodiment is shown in. Specifically, the occluderis collapsed and disposed within the delivery sheath. In this embodiment, the attachment memberis recessed within the frame. In some embodiments, a delivery device may further include a through-lumen or other such component that is configured to advance a distal end of the occluder, such as the distal annular flange, which may facilitate deployment and/or repositioning of the distal annular flange.

With reference now to, another embodiment of an occluderis illustrated. In this embodiment, the frameis formed from a single layer of braided shape-alloy wire material (e.g., nitinol). The braided wire material is cut and terminated to form the framein a tube or doughnut-like shape. Methods for cutting, shaping, and forming such braided wire frames are described in further detail in International Patent Application Publication No. WO2018/204106, which is incorporated herein by reference in its entirety.

In this embodiment, the closureis at least partially enclosed or folded within a pocketformed by the distal annular flange, as depicted in. The closuremay be folded within the distal annular flangeas the frameis constructed (e.g., before the frameis heat-set and/or cut), such as by being temporarily coupled to the material (e.g., the cut wire ends) forming the distal annular flangebefore the distal annular flangeis heat-set into its final form. Alternatively, the closuremay be “installed” into the distal annular flangeafter the frameis formed (e.g., by inserting the outer edge of the closureinto the pocket). A separate closuremay be similarly coupled to the framewithin the proximal annular flange. Another closuremay be coupled to the framewithin the passageway(e.g., coupled to the waist member).

As shown particularly in(which are a top and bottom view, respectively, of the occluder), the radially inner surfaceof the annular flanges,includes a scalloped edge including the cut wire ends. In some other embodiments, though not shown, at least some of these cut wire endsmay include eyelets or other attachment mechanisms that facilitate attaching the closurethereto and/or that act as an attachment memberof the occluderto facilitate advancement, recapture, an/or repositioning of the occluderduring deployment thereof.

In some cases, the cut wire endsof the framethat form the radially inner surfaceof the distal annular flange, as shown in, are exposed. To reduce a risk of thrombus from the cut wire ends, and to protect the cut wire endsas the occluderis deployed, the cut wire endsmay be fed through the closure, as shown in. For example, a slitmay be formed in the closurethrough which cut wire endsare positioned, such that the cut wire endsare enclosed by the closure. In some such embodiments, the cut wire endsmay be subsequently sewn or otherwise coupled to the closureto prevent relative movement between the closureand the cut wire ends. The length of the cut wire endsto be enclosed by the closureand/or the tightness of the coupling of the cut wire endsto the closuremay be selected to avoid interference with the ability of the frameto collapse and expand.

As shown in, the proximal annular flangeincludes three spokesthat are coupled to the cut wire endsand extend into the passageway. The attachment memberis coupled to the spokesat a central location with respect to the proximal annular flange. Moreover, as best seen in, the spokesare oriented at an oblique angle with respect to the planar surface of the proximal annular flange, such that the attachment memberis recessed into the frame. In this embodiment, the spokesdefine three equally-sized “access ports”to the passageway.

An alternative embodiment of the occluderis illustrated in. In this embodiment, the spokeshave different lengths and terminate at a non-central location with respect to the proximal annular flange. Accordingly, the attachment memberis coupled to the frameat this non-central location. In this embodiment, the spokesmay interfere less with the passagewayby defining one access portthat is substantially larger than the access ports(shown in).

depicts another embodiment of an occluderin accordance with the present disclosure. In this embodiment, the waist memberforms an angle with respect to the distal annular flange, and the proximal annular flangeis not planar but concave. This alternative shape for the waist memberand the proximal annular flangemay promote endothelialization and/or integration into the tissue of the septal wall. One or more closuresmay be coupled to the frameat the outer surfaces of the annular flanges,adjacent to the radially outer surface, as shown in dashed lines. Alternatively, closuresmay be coupled to the frameadjacent to the radially inner surfaceof the annular flanges,, as shown in dotted lines.

Although the waist memberhas been illustrated as conforming to the shape and/or size of the defect or tissue in which the occluderis deployed, it is contemplated that the waist membermay be smaller than the defect and/or non-centrally located within the defect. In addition, the annular flanges,may have alternative shapes and/or sizes than those shown herein, including irregular shapes and/or shapes that are not concentric or coaxial with the waist member. Moreover, the shape, size, and/or configuration of one annular flange,may differ from that of the other annular flange,.

Turning now to, an alternative embodiment of a frameof the occluderis shown. Specifically, the frameis formed as a laser-cut frame (contrasted with a braided frame as previously shown). The frameis first laser cut, as shown in(a side and top view, respectively), from a nitinol tube. The ends of the tube are then folded over to form flanges,of the frame, as shown in(a side and top view, respectively). The flanges,(as well as a waist member) are formed from a single layer of material, which may reduce the overall profile of the occluder. An attachment memberis coupled to the ends at the proximal annular flange. Closures,are coupled to the flanges,.

depict a side view and top view, respectively, of another occluderin accordance with the present disclosure. The occluderincludes a frameformed as a laser-cut frame, as described above, and/or from a plurality of wound wires. In this embodiment, annular flanges,are formed from heat-set, curled, free wire ends. Specifically, the framemay be formed as shown in. In particular, the framemay include distal free wire endsand proximal free wire ends. In some embodiments, the proximal free wire endsmay include attachment mechanisms, such as eyelets or hooks. As shown in, the free wire ends,are heat-set into curls. Closuresare coupled to the frameat one or more longitudinal positions between annular flangesand. For example, a distal closureis coupled to the framegenerally adjacent to the distal annular flange, and a proximal closure is coupled to the framegenerally adjacent to the proximal annular flange.